linux-kernel - Re: [PATCH 1/1] pci: expose SMBus on Asus notebook A6L

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Date:	Wed, 27 May 2009 11:59:10 +0200
From:	Mats Erik Andersson <mats.andersson@...ladisker.se>
To:	jbarnes@...tuousgeek.org
Cc:	linux-kernel@...r.kernel.org, trivial@...nel.org
Subject: Re: [PATCH 1/1] pci: expose SMBus on Asus notebook A6L

Some hardware observation on my suggested patch.

tisdag den 12 maj 2009 klockan 17:27 skrev Robert Hancock detta:
> Mats Erik Andersson wrote:
> >From: Mats Erik Andersson <mats.andersson@...ladisker.se>
> >
> >Addition of one unknown subsystem identifier to the
> >quirks handler for chipset i82855GM_HB on notebook
> >Asus A6L. This exposes the otherwise hidden SMBus
> >controller within the south bridge ICH4-M.
> >
> >Signed-off-by: Mats Erik Andersson <mats.andersson@...ladisker.se>
> >---
> >
> >Tried and successfully used on kernel 2.6.29 and 2.6.23.17.
> >
> >--- drivers/pci/quirks.c.orig	2009-05-09 00:47:21.000000000 +0200
> >+++ drivers/pci/quirks.c	2009-05-12 11:20:04.000000000 +0200
> >@@ -1068,8 +1068,9 @@ static void __init asus_hides_smbus_host
> > 		else if (dev->device == PCI_DEVICE_ID_INTEL_82855GM_HB)
> > 			switch (dev->subsystem_device) {
> > 			case 0x1751: /* M2N notebook */
> > 			case 0x1821: /* M5N notebook */
> >+			case 0x1897: /* A6L notebook */
> > 				asus_hides_smbus = 1;
> > 			}
> > 		else if (dev->device == PCI_DEVICE_ID_INTEL_82855PM_HB)
> > 			switch (dev->subsystem_device) {
> 
> This has to be done with caution. If the BIOS accesses the SMBus 
> controller from ACPI AML code or SMI code, then allowing a Linux driver 
> to access the controller may cause problems.

My notebook Asus A6L can use the driver it87-isa without any
modification to the vanilla kernel, but that only exposes the
fan sensors and it only claims 0 RPM for all three measurements.
I have been dissatisfies with the fan control for three years now,
since it never completely slows down!

When exposing the hidden SMBus, thus using driver max6657-i2c,
the temperature sensors for motherboard and cpu becomes accessible
for lm-sensors for the first time. However, this cpu temperature
coincides with the claims done by the proc-acpi entry. 

I am since some time now using a recompiled kernel with my suggested
patch activated, and I have as of yet not noticed any difference
in system behaviour. On the other hand I still cannot silence
the fan.

Regards

Mats Erik Andersson

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